Why was shii strong in the beginning but later just turned stupid?

Ikr?!

Love. Feelings. Attachment. Her heart is foolish, so...
Well, it wouldn't be good if she just gave up.
Stupid or otherwise, I want her to go on and do the stuff she does best.
I don't want her to abandon her master, strangely enough, even if I dislike those types of guys the most. Because... I understand how she feels.